lapatinib

What is the most important information I should know about lapatinib?

Do not use lapatinib if you are pregnant. It could harm the unborn baby.

Lapatinib can cause severe or fatal liver problems. Call your doctor at once if you have: upper stomach pain, itching, dark urine, clay-colored stools, or jaundice (yellowing of the skin or eyes).

What is lapatinib?

Lapatinib is used to treat advanced hormone-related breast cancer that has progressed or spread after treatment with other cancer medicines.

Lapatinib is used for this condition only if your tumor tests positive for a protein called human epidermal growth factor receptor 2 (HER2). HER2 protein can speed the growth of cancer cells.

In postmenopausal women, lapatinib is given in combination with a hormonal medicine called letrozole (Femara). In others, lapatinib is given together with a cancer medicine called capecitabine (Xeloda).

Lapatinib may also be used for purposes not listed in this medication guide.

What should I discuss with my healthcare provider before taking lapatinib?

You should not use lapatinib if you are allergic to it.

Tell your doctor if you have ever had:

heart disease;

liver disease (lapatinib can cause severe or fatal liver problems);

an electrolyte imbalance (such as low levels of potassium or magnesium in your blood); or

long QT syndrome (in you or a family member).

You may need to have a negative pregnancy test before starting this treatment.

Both men and women using this medicine should use effective birth control to prevent pregnancy. Lapatinib can harm an unborn baby or cause birth defects if the mother or father is using this medicine. Keep using birth control for at least 1 week after your last dose.

Tell your doctor right away if a pregnancy occurs while either the mother or the father is using lapatinib.

Do not breast-feed while using this medicine, and for at least 1 week after your last dose.

How should I take lapatinib?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

When used with letrozole, the usual dose of lapatinib is 6 tablets taken once daily every day. Letrozole is also taken every day.

When used with capecitabine, the usual dose of lapatinib 5 tablets taken once daily for 21 days in a row. Capecitabine is also taken twice daily for only the first 14 days. This 21-day cycle is then repeated.

Follow your doctor's dosing instructions very carefully.

Take lapatinib on an empty stomach, at least 1 hour before or 1 hour after a meal.

You may swallow each lapatinib tablet one at a time, but take the entire dose (all 5 or 6 tablets) at the same time each day.

Capecitabine must be taken with food or within 30 minutes of eating.

You will need blood tests every 4 to 6 weeks to check your liver function. Your heart function may also need to be checked using an electrocardiograph or ECG (sometimes called an EKG).

Store lapatinib at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use.

Your doctor will determine how long to treat you with lapatinib and capecitabine or letrozole. Take your medications for the full prescribed length of time. Combination chemotherapy is usually continued unless your condition gets worse or you have serious side effects.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking lapatinib?

Grapefruit may interact with lapatinib and lead to unwanted side effects. Avoid the use of grapefruit products.

What are the possible side effects of lapatinib?

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

new or worsening cough, wheezing, chest pain, feeling short of breath.

Common side effects may include:

indigestion, loss of appetite;

nausea, vomiting, diarrhea;

rash, itching, dry skin, acne;

pain or redness on the palms of your hands or the soles of your feet;

problems with your fingernails or toenails;

feeling weak or tired;

nosebleeds, mouth sores;

thinning hair; or

headache.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect lapatinib?

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.

Many drugs can affect lapatinib. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any medicine you start or stop using.

Where can I get more information?

Your doctor or pharmacist can provide more information about lapatinib.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

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